Setting member for heating material

ABSTRACT

A setting member for a heating material formed by sintering and heating a base and a coating layer at 1300 DEG  to 1550 DEG  C., in which the base comprises at least one selected from the group consisting of Al2O3, MgO and ZrO2 in an amount of 70 wt % or more, the coating layer contains at least one main component selected from the group consisting of Al2O3, MgO and ZrO2 in an amount of 80 wt % or more and 0.5 to 10.0 wt % of at least one additional component selected from Fe2O3, TiO2, BaO, SrO, ZrO2, CaO, and MgO (different from CaO and MgO used as a stabilizer for ZrO2) excluding the same types of the additional component as used in the main component of the coating layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a setting member for use in heating orsintering (hereinafter, referred to as "heating") ferrite and functionalceramics such as a ceramic condenser. More particularly, the presentinvention relates to a setting member comprising a base refractory and ahard coating layer firmly coated on the base refractory partially or inits entirety and which is hardly peeled off or abraded even if thesetting member is repeatedly heated and cooled.

2. Description of the Related Art

Hitherto, a setting member, such as a rack or a vessel, has been widelyused in heating ferrite and electric parts made of functional ceramicssuch as ceramic condenser. The setting member comprises a baserefractory (hereinafter referred to as "base") formed of Al₂ O₃ and aZrO₂ coating layer.

Since ZrO₂ has a high density, a setting member formed of ZrO₂ alone isvery heavy. Then, if a light-weight setting member is desired most, itwill be better to use ZrO₂ only in a coating layer. Furthermore, sinceZrO₂ is less reactive to a relatively wide variety of heating materials,it is suitable for use in a coating layer. On the other hand, the Al₂ O₃base material, if used together with SiO₂, exhibits excellentproperties, easy to sinter and hard to break, as is known in prior art.However, SiO₂ is not preferable for a heating material. Direct contactof SiO₂ with a heating material must be avoided.

For these reasons, a setting member comprising the Al₂ O₃ base materialand ZrO₂ coating layer, which may be formed on the surface of the baseby various methods, has been conventionally and widely used. If thecoating layer is made of ZrO₂ alone by heating, the resultant layer willbe easily peeled off from a base since ZrO₂ is converted from amonocrystal form to a tetracrystal form at about 1100° C. Therefore, inmost cases, ZrO₂ is used after partially stabilized with CaO or Y₂ O₃into a tetracrystal form.

However, there is a problem in the setting member formed of an Al₂ O₃base and a ZrO₂ coating layer formed on the surface of the basepartially or in its entirety by the aforementioned method. That is,after the setting member is used many times, the ZrO₂ coating layer ispeeled off or abraded. As a result, the removed ZrO₂ particles bond on aheated material. Hence, it has been strongly desirable to furtherimprove the resistance of the coating layer.

The ZrO₂ layer may be mechanically peeled off or abraded due to thedifference in thermal expansibility between the base and the ZrO₂coating layer and due to the reaction taken place between ZrO₂ andcomponents contained in a functional ceramic when the functional ceramicis placed on the setting member and heated. Various proposals have beenpreviously proposed to prevent the removal or abrasion of the ZrO₂layer, but all of them are unsatisfactory. The conventionally knownproposals for preventing the mechanical removal or abrasion of the ZrO₂layer are classified into the following four methods:

A first method is a press molding method as proposed in Jpn. Pat. Appln.KOKOKU Publication No. 60-51426. In this method, a ZrO₂ layer having 10to 50 wt % weight relative to the total weight of the bottom thickness,is placed on the bottom of a container made of Al₂ O₃ --SiO₂. Then, theAl₂ O₃ --SiO₂ base and ZrO₂ layer are pressed and molded to form anintegral structure. In this manner, the Al₂ O₃ --SiO₂ base is coatedwith the ZrO₂ coating layer.

This method is advantageous in forming a ZrO₂ layer thick enough toprevent the peeling of the ZrO₂ layer, but it hardly applies the ZrO₂coating layer to the entire base surface. If the entire base surface iscoated with the ZrO₂, the resultant setting member will be too heavy tohandle.

In a second method, various improvements are provided to the ZrO₂ layeritself. For example, in Jpn. Pat. Appln. KOKAI Publication No. 3-223193,an intermediate layer formed of ZrO₂ partially stabilized with Y₂ O₃ isinterposed in the middle of the ZrO₂ coating layer, to improve the peelresistance of the ZrO₂ coating layer. In Jpn. Pat. Appln. KOKAIPublication No. 3-177379, a desired number of Al₂ O₃ /ZrO₂ coatinglayers are provided on the surface of an alumina base. The Al₂ O₃ /ZrO₂coating layers are designed to have a molar ratio of Al₂ O₃ to ZrO₂which is gradually decreased from the base side toward the outer side.Jpn. Pat. Appln. KOKAI Publication No. 4-224172 discloses an zirconiadiffusion layer which is interposed between an Al₂ O₃ base and azirconia coating layer.

However, in Publication Nos. 3-223193 and 3-177379, the peel resistanceof the ZrO₂ layer is not satisfactory since the ZrO₂ layer ismechanically bonded but not chemically.

Furthermore, in Publication No. 4-224172, the solid-solution of ZrO₂ isslightly present in the Al₂ O₃ base, however, a reaction product betweenZrO₂ and Al₂ O₃ is not yielded. Therefore, ZrO₂ and Al₂ O₃ aresubstantially bonded in a mechanical manner, so that the bondingstrength is unsatisfactory.

A third method is one in which ZrO₂ particles are bonded on the surfaceof a base by use of an adhesive agent after molding or sintering. Forexample, in Jpn. Pat. Appln. KOKAI Publication No. 63-25487, a zirconiapowder is bonded on a base via an alumina slurry and the resultantstructure is heated to coat the ZrO₂ layer on the base. Jpn. Pat. Appln.KOKAI Publication No. 64-89510 disclose a ZrO₂ layer formed by bondingZrO₂ particles with an inorganic glass binder. Furthermore, Jpn. UM.Appln. Publication No. 57-91099 discloses a ZrO₂ layer formed of azirconia powder by bonding the zirconia powder on the surface of a basevia a vitrification substance acting at a low melting point.

However, the third methods are unfavorable since zirconia particles falloff. More particularly, this method is unfavorable since Si is the maincomponent of an inorganic glass binder.

A fourth method is a flame-spray method. In this method, ZrO₂ isflame-sprayed into the sintered base to simultaneously bond ZrO₂ on thebase. In Jpn. Pat. Appln. KOKOKU Publication No. 4-586, partiallystabilized zirconia is repeatedly flame-sprayed on a base while thecontent of CaO is gradually increased. In Jpn. Pat. Appln. KOKOKUPublication No. 3-77652, the thermal expansibility of a base becomesnearly equal to that of a coating material through flame-spray ofpartially stabilized zirconia.

The coating layer obtained by the flame-spray method is dense enough toprevent a reaction with a heating material. However, the flame-spraymethod is not satisfactory to prevent peeling of the ZrO₂ layer sincethe flame-spray is not basically a chemical reaction.

The flame-spray method converts the a component of a base and a coatinglayer in quality. As a result, a heating material may react with theconverted base component or coating component. Moreover, depending onthe type of the heating material, the setting member obtained by use ofthe flame-spray cannot be used. Furthermore, the flame spray method hasa problem in that it requires a specific apparatus and material.

Another technique of the flame-spray method using zirconia is disclosedin Jpn. Pat. Appln. KOKOKU Publication No. 4-21330. In this method, anAl₂ O₃ flame-spray layer is formed between a base and zirconia coatinglayer. However, due to a multi-layered structure, this method raisescost. As is mentioned above, there are various proposals in the priorart but any one of the proposals is unsatisfactory.

More specifically, ZrO₂ is low in reactivity and hardly sintered to bondto a base, unlike alumina and mullite refractory materials. To obtain asufficiently strong structure, the ZrO₂ layer must be heated atrelatively high temperature, e.g., 1600° C. or more. To bond a ZrO₂layer to the base, the higher temperature the ZrO₂ layer is heated at,the larger distortion between the base and the ZrO₂ coating layer isgenerated, ascribed to the different thermal expansion therebetween. Asa result, problems such as peeling and cracks are likely to occur afterthe heating.

To prevent the peeling and cracks, if ZrO₂ is heated at low temperature,sufficient strength of the ZrO₂ layer will not be obtained. As a result,peeling and particle removal also take place due to friction.

As prior art other than a zirconia-coated setting member, a ferrite-coreheating case is disclosed in Jpn. Pat. Appln. KOKOKU publication No.5-47505, and a heating setter is disclosed in Jpn. Pat. Appln. KOKOKUpublication No. 1-24745. The ferrite-core heating case is made offerrite, mullite and zirconia. Owing to the addition of ferrite, the lowreactivity is overcome but a heating material is inevitably exposed tomullite. In this respect, this method is unsatisfactory.

The heating setter is formed by heating a mixture of aspinelle-structure ferrite and a non-spinelle structure ferrite. Sincethe heating setter has a porosity of 15 to 40%, it is not suitable foruse in the coating layer. In addition, the strength of the heatingsetter is low, so that peeling is liable to occur and the abrasionresistance is low.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide a setting member for aheating material, which comprises a base and a coating layer havingexcellent hardness, bonded on the surface of a base, partially or in itsentirety. According to the present invention, there is provided asetting member for a heating material having a coating layer which ishardly abraded and peeled off even if it is repeatedly exposed to hightemperatures.

In one aspect of the present invention, there is provided a settingmember for a heating material comprising a base and a coating layerformed on a surface of the base partially or in its entirety, in whichthe base comprises at least one main component selected from the groupconsisting of Al₂ O₃, MgO and ZrO₂ in an amount of 70 wt % or more andthe coating layer comprises at least one main component selected fromthe group consisting of Al₂ O₃, MgO and ZrO₂ in an amount of 80 wt % ormore and 0.5 to 10.0 wt % of at least one additional component selectedfrom Fe₂ O₃, TiO₂, BaO, SrO, CaO, and MgO (different from CaO and MgOused as a stabilizer for ZrO₂) excluding the same type of the additionalcomponent as used in the main component of the coating layer.

To be more specific, the main component of the base may comprise atleast one selected from the group consisting of ZrO₂ partiallystabilized with CaO, ZrO₂ partially stabilized with MgO, and ZrO₂partially stabilized with Y₂ O₃.

A main component of the base may comprise unstabilized ZrO₂ and at leastone selected from the group consisting of ZrO₂ partially stabilized withCaO, ZrO₂ partially stabilized with MgO, and ZrO₂ partially stabilizedwith Y₂ O₃.

The base may comprise Al₂ O₃ as a main component and a coating layer maycomprise Al₂ O₃ as a main component and Fe₂ O₃ as an additionalcomponent.

The base may comprise Al₂ O₃ as a main component, the coating layer maycomprise Al₂ O₃ as a main component and Fe₂ O₃ and CaO as an additionalcomponent.

The base may comprise Al₂ O₃ as a main component and the coating layermay comprise Al₂ O₃ as a main component and TiO₂ as an additionalcomponent.

The base may comprise Al₂ O₃ as a main component and the coating layermay comprise unstabilized ZrO₂ and/or partially stabilized ZrO₂ as amain component, and BaO and/or SrO, and TiO₂ as an additional component.

The base may comprise Al₂ O₃ as a main component, the coating layer maycomprise unstabilized ZrO₂ and/or partially stabilized ZrO₂ as a maincomponent, and BaO and/or SrO, TiO₂ and CaO (different from CaO used instabilizing ZrO₂) as an additional component.

The base may comprise Al₂ O₃ as a main component, the coating layer maycomprise unstabilized ZrO₂ and/or partially stabilized ZrO₂ as a maincomponent, and Fe₂ O₃ and CaO (different from CaO used in stabilizingZrO₂) as an additional component.

The coating layer may comprise at least one main component selected fromthe group consisting of ZrO₂ stabilized with MgO, ZrO₂ stabilized withCaO, and ZrO₂ stabilized with Y₂ O₃.

The coating layer may comprise an unstabilized ZrO₂ and at least oneselected from the group consisting of ZrO₂ stabilized with MgO, ZrO₂stabilized with CaO, ZrO₂ stabilized with Y₂ O₃ as a main component.

ZrO₂ used as a main component of the coating layer may be unstabilizedZrO₂.

The coating layer may comprise particles having 0.1 mm in diameter orless in an amount of 50 wt % or more.

According to another aspect of the present invention, there is provideda setting member for a heating material in which a coating layer havingexcellent hardness is tightly bonded to the entire or partial surface ofa base. Owing to the excellent hardness of the coating layer, thesetting member is hardly abraded and peeled when exposed to hightemperatures.

The setting member for a heating material of the present invention canbe manufactured by the steps of: molding raw material comprising atleast one main component selected from the group consisting of Al₂ O₃,MgO and ZrO₂, and heating the molded raw material to form a base,

coating the surface of the base partially or in its entirety with acoating material comprising a main component, ZrO₂ in an amount of 80 wt% or more, and at least one additional component selected from the groupconsisting of Fe₂ O₃, TiO₂, BaO, SrO, CaO, and MgO (different from CaOand MgO used as a stabilizer for ZrO₂) in an amount of 0.5 to 10.0 wt %,in which the coating material comprises particles of 0.1 mm or less indiameter in an amount of 50 wt % or more; and

drying the base coated with the coating material and heating orsintering (hereinafter, referred to as "heating") at 1300° to 1550° C.

The setting member of the present invention may be manufactured byemploying the base comprising Al₂ O₃ as a main component, and thecoating material comprising unstabilized ZrO₂ and/or ZrO₂ partiallystabilized with CaO as a main component and TiO₂, BaO, SrO and CaO(different from CaO used in stabilizing ZrO₂) as an additionalcomponent.

The setting member may be manufactured by employing the base comprisingAl₂ O₃ as a main component, and the coating material comprisingunstabilized ZrO₂ and/or ZrO₂ partially stabilized with CaO as a maincomponent and Fe₂ O₃ and CaO (different from CaO in stabilizing ZrO₂) asan additional component.

The setting member may be manufactured even if ZrO₂ serving as a maincomponent of the base is partially stabilized ZrO₂.

The setting member may be manufactured even if ZrO₂ serving as a maincomponent of the base is partially stabilized ZrO₂ and unstabilizedZrO₂.

According to the present invention, as the coating layer becomes harder,the bonding between the base and coating layer becomes stronger. Owingto this feature, the abrasion and peeling of the coating layer isreduced more than those of the conventional setting material, even if aheating material such as a ceramic condenser or ferrite is repeatedlyheated while heating and cooling are being repeated.

Furthermore, the heating material cannot be degraded since the coatingmaterial does not react with a heating material.

Moreover, a long-life setting member can be obtained, contributing tocost saving.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention and, together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a diagram showing a state of Al₂ O₃ --TiO₂ series; and

FIG. 2 is a view of an apparatus for use in an abrasion resistance testof the ceramic material used in the setting member for a heatingmaterial, obtained in the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The setting member for a heating material of the present invention isformed by coating a coating layer on a base partially or in its entiretyand heating the base coated with a coating layer, in which

the base comprises at least one main component selected from the groupconsisting of Al₂ O₃, MgO and ZrO₂ and

the coating layer comprises (at least one main component selected fromthe group consisting of Al₂ O₃, MgO and ZrO₂) at least one additionalcomponent selected from Fe₂ O₃, TiO₂, BaO, SrO, CaO, and MgO.

The base used herein must contain at least one component selected fromthe group consisting of Al₂ O₃, MgO and ZrO₂, in an amount of 70 wt % ormore. If the component is contained in an amount less than 70 wt %, itis not preferable since the content of SiO₂ is relatively increased.

The base including Al₂ O₃ as a main component is formed by molding Al₂O₃ powder, sintering the molded Al₂ O₃ powder at 1600° C. or more.Alternatively, the base may be formed by adding an alumina silicate suchas mullite, andalsite, sillimanite or kaolin to the Al₂ O₃ powder andsintering the mixture at a temperature from 1300° to 1750° C.

It is preferred that ZrO₂ may be at least one selected from the groupconsisting of ZrO₂ partially stabilized with CaO, ZrO₂ partiallystabilized with MgO, and ZrO₂ partially stabilized with Y₂ O₃. However,depending on types or usages of a heating material, ZrO₂ may be amixture of an unstabilized ZrO₂ and at least one of partially stabilizedZrO₂ selected from the group consisting of the aforementioned threetypes of ZrO₂. When the ZrO₂ mixture is used, the partially stabilizedZrO₂ is preferably contained in an amount of 50 wt % or more. The basecannot be formed of unstabilized ZrO₂ alone.

The base can be formed of MgO alone. The base may be formed by sinteringa mixture of MgO and spinelle or a mixture of MgO, spinelle and ZrO₂, ata temperature from 1550° to 1700° C. The base made of the aforementionedmaterials has a strong heat resistance during heat treatment and lessharmful influence on a heating material.

The coating layer may be formed on the entire surface of the base thusobtained or partially on the surface contact with a heating material.

The coating layer used herein may comprise at least one main componentselected from the group consisting of Al₂ O₃, MgO and ZrO₂. The maincomponent of the coating layer may be the same as or different from thatof the base.

ZrO₂ used as the main component of the coating layer may be at least oneselected from the group consisting of ZrO₂ partially stabilized withCaO, ZrO₂ partially stabilized with MgO, and ZrO₂ partially stabilizedwith Y₂ O₃, a mixture of unstabilized ZrO₂ and at least one partiallystabilized ZrO₂ selected from the group consisting of aforementionedthree types of partially stabilized ZrO₂, or unstabilized ZrO₂ alone.

The main component of the coating layer used herein must include atleast one component selected from the group consisting of Al₂ O₃, MgOand ZrO₂ in an amount of 80 wt % or more. If the main component iscontained in an amount less than 80 wt %, it is not preferable sinceSiO₂ liable to react with a heating material is relatively increased inthe amount.

The coating layer may include the aforementioned main component and atleast one additional component selected from Fe₂ O₃, TiO₂, BaO, SrO,CaO, and MgO which are unrelated with CaO and MgO used as a stabilizerfor ZrO₂. It should be noted that the additional component can not bethe same as the main component of the coating layer. To be morespecific, when MgO is employed as the main component of the coatinglayer and as an additional component, it produces no effect. When MgO isemployed, at least one additional component must be selected from Fe₂O₃, TiO₂, BaO, SrO, and CaO except MgO.

The additional component may be contained in the coating material in anamount of 0.5 to 10.0 wt %. If the content of the additional componentis less than 0.5 wt %, the coating layer may fail to tightly bond to abase. The coating layer thus obtained is liable to be peeled off and lowin hardness and abrasion resistance. As a result, the setting memberwill not be obtained in good quality. In contrast, if the content of theadditional component exceeds 10 wt %, the resultant coating layer willbe extremely dense. As a result peeling also occurs when the coatinglayer is heated together with a heating material. Furthermore, reactionwith a heating material is easily taken place. The additional componentmay be contained at an amount within the aforementioned range inaccordance with types of the base and heating material. For example, Fe₂O₃, BaO and TiO₂, even in a relatively small content, can produceeffects. MgO or SrO may be added in a relatively large amount.

Of the particles of the components forming the coating layer, theparticles having 0.1 mm or less in diameter are preferably contained inan 50 wt % or more. If the amount of particles having 0.1 mm or less indiameter is less than 50 wt %, it is not preferable since sufficienthardness of the coating layer cannot be obtained. To offset the decreasein hardness, it may be effective to increase the content of theadditional component. However, if so, the content of the additionalamount exceeds the upper limit (10 wt %) limited by the presentinvention from the viewpoint of preventing the reaction with a heatingmaterial.

Hereinbelow, we will give examples of preferable combinations of themain components of the base and the coating layer and the additionalcomponent of the coating layer, which should be chosen in accordancewith a type of a heating material or the like.

When Al₂ O₃ is used as the main component of the base, the followingcombinations may be employed as the coating layer:

1. Main component: Al₂ O₃

Additional component: Fe₂ O₃ (1 to 6 wt %)

2. Main component: Al₂ O₃

Additional component: Fe₂ O₃ and CaO (1.5 to 7.5 wt % in total)

3. Main component: Al₂ O₃

Additional component: TiO₂ (0.5 to 5.5 wt %)

4. Main component: unstabilized ZrO₂ and/or Partially stabilized ZrO₂with CaO

Additional component: Either BaO and/or SrO and TiO₂ (3 to 5 wt % intotal)

5. Main component: unstabilized ZrO₂ and/or Partially stabilized ZrO₂with CaO

Additional component: Either BaO and/or SrO and TiO₂ (3 to 5 wt %) andCaO* (1 to 3 wt %)

6. Main component: unstabilized ZrO₂ and/or Partially stabilized ZrO₂with CaO

Additional component: Fe₂ O₃ and CaO* (1 to 7.5 wt % in total)

* CaO is different from CaO used as a stabilizer for ZrO₂

When TiO₂ is added together with BaO and SrO, they may be addedsimultaneously in the form of a compound such as BaTiO₃ and SrTiO₃. In asimilar way, they are added in the form of a compound such as BaCO₃ andSrCO₃, CaCO₃ since they can convert into BaO, SrO and CaO shown in claim1 after heating.

The additional component, even if added in a small amount, produceshighly advantageous effects such as improvements in strength of thecoating layer itself, in binding strength between the coating layer andthe base and in abrasion resistance of the coating layer. Therefore,when the setting member of the present invention is repeatedly subjectedto heating and cooling, abrasion, particle removal, and peeling of thecoating layer are scarcely observed, increasing its lifetime. The causesof such advantageous effects are not exactly elucidated but presumablyconsidered as follows:

If a coating layer comprises at least one main component selected fromthe group consisting of Al₂ O₃, MgO, and ZrO₂ as the main component inthe coating layer and an additional component selected from the groupconsisting of Fe₂ O₃, TiO₂, BaO, SrO and the like, the solid solutionreaction will take place between Al₂ O₃ and MgO or ZrO₂ in the coatinglayer or between the coating material and the base, at a heatingtemperature of near 1500° C. As a result, a compound or a liquid phaseis rapidly produced.

When Al₂ O₃ is reacted with TiO₂, Al₂ TiO₅ is produced at hightemperature as shown in FIG. 1 but it will be decomposed into TiO₂ andαAl₂ O₃ at low temperature. However, in the case where coating layer ofabout 1 mm in thickness is present on the surface of the base, as is inthe present invention, the coating layer is cooled relatively fasterthan the inside portion of the base, so that a compound stable at onlyhigh temperature is considered to be present at normal temperature inthe coating layer. As explained above, the presence of the compound inthe base contributes to improvements of binding strength and abrasionresistance of the coating layer.

In the combination of Fe₂ O₃ and TiO₂ as an additional component and Al₂O₃, MgO and ZrO₂ as main components of the base material and coatingmaterial, the solid phase is partially formed on the surface of aparticle of the main component and it probably acts as an auxiliaryagent for bonding through heating. It has been conventionally known thata compound liable to produce a compound having a low melting point, suchas SiO₂, Na₂ O, K₂ O, or B₂ O₃ acts as an auxiliary agent. However sucha compound is susceptible to react with a heating material and degradesthe quality of the coating layer during heat treatment. The coatinglayer used in the present invention hardly reacts with a heatingmaterial and therefore the strength of the coating layer is scarcelylowered by heat treatment.

The invention of claim 14 of the present invention is directed to amethod for producing a setting member for a heating material. In thisinvention, a base is formed by molding a raw material comprising atleast one main component selected from the group consisting of Al₂ O₃and MgO or ZrO₂ into a predetermined form and by sintering the moldedmaterial. The raw material and sintering temperature are the same aspreviously described.

Then, a coating material is coated on the surface of the base partiallyor in its entirety. The coating layer is formed of a main componentcontaining ZrO₂ in an amount of 80 wt % or more and at least oneadditional component selected from the group consisting of Fe₂ O₃, TiO₂,BaO, SrO, CaO and MgO, (different from CaO, MgO used as a stabilizer forZrO₂) in an amount of 0.5 to 10.0 wt %. The coating layer may becontained particles having 0.1 mm or less in an amount of 50 wt % ormore.

ZrO₂ serving as a main component of the coating layer may be at leastone selected from the group consisting of ZrO₂ partially stabilized withCaO, ZrO₂ partially stabilized with MgO, and ZrO₂ partially stabilizedwith Y₂ O₃, may be unstabilized ZrO₂ or may be a mixture of unstabilizedZrO₂ and at least one selected from the group consisting of theaforementioned three types of partially stabilized ZrO₂.

As the additional component, a component inevitably contained in the rawmaterial is not effective. Therefore, even if the same component iscontained in the raw material, the additional component must be addedindependently. The additional component and the main component of thecoating material must be mixed to disperse uniformly to each other andpreferably mixed in a ball mill. The raw material of the coatingmaterial is preferably formed of particles having 0.1 mm or less in anamount of 50 wt % or more so as to impart sufficient hardness to thecoating layer.

The base may be coated by the coating material by pouring or spraying aslurry of the coating material on the base. Thereafter, the coatingmaterial is bonded to the base by heating. Alternatively, the coatingmaterial may be flame sprayed into the base. The coating material may beformed in a thickness of 0.2 to 1 mm, in the same manner for use informing a conventional setting member for a heating material. Thecoating material is heated at a low temperature in the range from 1300°to 1550° C., preferably from 1350° to 1450° C. Through the heating, thebase can be tightly bonded to the coating layer, so that the coatinglayer is scarcely abraded and peeled off even if heating and cooling isrepeated.

Hereinbelow, the setting member of the present invention will beexplained with reference to examples.

(EXAMPLES 1-6 AND COMPARATIVE EXAMPLES 1-4)

In the Examples 1-6, the plate-like base of a setting member for aheating material was formed from Al₂ O₃ powder having a purity of 99.9%in an amount of 70 to 80 wt % SiO₂ and a component inevitably containedin the powder. The raw material powder was molded and sintered at 1450°C. to obtain the base of a setting member whose external size of 150mm×150 mm×8 mm, as shown in Table 1.

On the other hand, a coating material was prepared by adding additionalcomponents (shown in Table 1) to main component, ZrO₂ partiallystabilized with CaO. Of the particles consisting of the coatingmaterial, particles having a diameter of 0.1 mm or less were set to becontained in an amount of 60 to 80 wt %.

The main component and additional component of the coating material weremixed uniformly in a ball mill. To the mixture thus formed, water wasadded in an amount of 25 to 40 wt % to make a slurry. Subsequently, theslurry was poured over the surface of the base to thereby form a coatinglayer of 1 mm in thick thereon. Thereafter, the base thus coated wasdried at 100° C. and in an electric furnace to 1400° to 1500° C.,thereby obtaining a setting member for a heating material.

In Examples 1 to 6, the main component, Al₂ O₃ was contained in anamount of 70 to 80 wt % in the base. The main component, ZrO₂ and anadditional component shown in table 1 were used in the coating materialin an amount of 85 to 93 wt % and 0.6 to 6.0 wt %, respectively. Itshould be noted that CaO used as an additional component in Example 5differs from CaO used for stabilizing ZrO₂ serving as the main componentof the coating material.

On the setting member thus obtained, a plurality of ferrite orcondensers were placed at random and repeatedly heated. Ferrite washeated at 1250° C. Ceramic condensers, Vristers and Pct thermistors wereheated at 1350° C. in Examples or comparative examples. The heating wasrepeated until the coating layer was peeled from the base and a crackwas generated in the setting member. The heating times repeated in bothcases were checked. The heating was terminated upon the removal of thecoating layer or upon the generation of a crack in the base. The resultsof Examples 1-6 are listed in Table 1, together with ComparativeExamples 1-4. In the column "Relevancy to a heating material", types andstates of heating materials are indicated.

In Tables 1 to 7, Examples having data of specific abrasion amount afterheating (10 times) with comments "particles of coating material arebonded or "no desired properties" means that the heating was terminatedafter heating was repeated 10 times. Furthermore, Examples having nodata of specific abrasion amount after heating (10 times) and no recordin "Heating cycles" means that heating was terminated after the settingmember was heating just once.

Using a plate-like test pieces formed of the same material as used inthe setting member of a heating material shown in Table 1, the abrasionresistance of the coating layer was tested, immediately after thecoating layer was bonded to the base by heating and after 10 timeheating-cooling cycle was applied to the coating layer at the sametemperature.

The abrasion resistance was tested by use of an apparatus shown in FIG.2. The apparatus is constructed as follows: On a holding plate 1, arotatable table 2 is mounted. To the rotatable table 2, a rotating axis3 is connected, thereby rotating the rotatable table 2. Test pieceholding plates 4 are immobilized on the rotatable table 2 byimmobilizing vises 5, While a test piece 9 was placed on the rotatabletable 2 and pressed on the surface by a pin 6, the rotatable table wasrotated. In this manner the abrasion amount of the test piece wasmeasured. In FIG. 2, reference numerals 7 and 8 are a pin holding memberand a load cell, respectively. Other conditions for the abrasion testare follows:

Size of a test piece*: 100φ×15 mm

Pin: 20φ (TiB₂)

Pressing Load: 2 kgf (0.6 kgf/cm²)

Abrasion rate: 21 cm/sec (100 r.p.m)

Abrasion distance: 2500 cm

Abrasion amount: the amount of reduced weight after test

* the surface of a test piece is made of ZrO₂ partially stabilized withCaO

As shown in Table 1, the coating layer of the setting members of thepresent invention shows extremely good abrasion resistance immediatelyafter the coating layer was bonded by heating, compared to the coatinglayer containing no additional component. As a result, it wasdemonstrated that a good coating layer is formed on the base in thepresent invention, since a large number of the heating times werecompleted until the coating layer was peeled off and until a crack wasmade in the setting member. Any additional component such as Fe₂ O₃,TiO₂, BaO, SrO, CaO, or MgO was used, the same results were obtained.Even if the additional component was added in an amount of 0.6%, thegood coating layer was successfully obtained.

In Comparative Examples 1 and 2, since the coating materials thereofcontained no addition components, the abrasion amounts were large in theabrasion test and coating particles were bonded onto the surface of acondenser as a heating material. The obtained coating layers were notsatisfactory. In Comparative Examples 3 and 4, Al₂ O₃ serving as a maincomponent was contained in the base in an amount of 60 wt %. The settingmembers obtained were also not satisfactory since warp was developed onthe setting member. The setting members were only used 18 times inheating-cooling cycles.

The setting members of all Examples and Comparative Examples on andafter Example 7 were manufactured by using components shown in thecorresponding Tables, and the same manufacturing method as in Examples1-6 except that the sintering and heating temperatures of the base andcoating material were appropriately chosen in accordance with the purityof the main component of the base and the properties of the maincomponent and additional component used in the coating material.

                                      TABLE 1                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       1     Al.sub.2 O.sub.3                                                                   70  ZrO.sub.2 --C*.sup.1                                                                93                                                                              80      Fe.sub.2 O.sub.3                                                                  6.0                                        2     Al.sub.2 O.sub.3                                                                   70    "   90                                                                              70      TiO.sub.2                                                                         4.0                                        3     Al.sub.2 O.sub.3                                                                   70    "   85                                                                              60      BaO 0.6                                        4     Al.sub.2 O.sub.3                                                                   75    "   88                                                                              60      SrO 3.0                                        5     Al.sub.2 O.sub.3                                                                   75    "   91                                                                              70      CaO 2.0                                        6     Al.sub.2 O.sub.3                                                                   80    "   89                                                                              75      MgO 2.0                                        Comparative                                                                   Example                                                                       1     Al.sub.2 O.sub.3                                                                   70  ZrO.sub.2 --C                                                                       98                                                                              85      None                                           2     Al.sub.2 O.sub.3                                                                   90  MgO   80                                                                              75      None                                                          Al.sub.2 O.sub.3                                                                    18                                                       3     Al.sub.2 O.sub.3                                                                   60   ZrO.sub.2 --C                                                                      90                                                                              80      BaO 5.0                                        4     Al.sub.2 O.sub.3                                                                   60   Al.sub.2 O.sub.3                                                                   80                                                                              75      Fe.sub.2 O.sub.3                                                                  3.0                                                        ZrO.sub.2 --C                                                                       4                                                       __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       1     60     72   48    No cracks until                                                                      Ferrite                                                                48 cycles                                             2     56     69   68    No cracks until                                                                      Condenser                                                              68 cycles                                             3     96     125  63    No cracks until                                                                      Condenser                                                              63 cycles                                             4     68     89   84    No cracks until                                                                      Condenser                                                              84 cycles                                             5     94     116  72    No cracks until                                                                      Ferrite                                                                72 cycles                                             6     162    206  78    No cracks until                                                                      Condenser                                                              78 cycles                                             Comparative                                                                   Example                                                                       1     2220   2850 --    --     Condenser*3                                                 or more*2                                                        2     1620   2400 --    --     Condenser*3                                    3     21     30   No peeling                                                                          42     Condenser                                                        until 42     Large warp                                                       cycles                                                      4     54     59   No peeling                                                                          No cracks until                                                                      Ferrite                                                          until 18                                                                            18 cycles                                                                            Large warp                                                       cycles                                                      __________________________________________________________________________     *1 ZrO.sub.2 --C . . . ZrO.sub.2 partially stabilized with CaO                *2 . . . Abrasion proceeded to a base material                                *3 . . . Particles of coating material adhere on the heating material    

(EXAMPLES 7-12 AND COMPARATIVE EXAMPLES 5-7)

The setting members were obtained by using materials shown in Table 2,in the same manner as in Examples 1-6. In Examples 7-12, Al₂ O₃ was usedas a main component, ZrO₂ partially stabilized with CaO was used as amain component of the coating material and two types of additionalcomponents were used.

As the additional components, Fe₂ O₃ and CaO which was different fromCaO used as a stabilizer for ZrO₂, were employed in an amount of 1.1 wt% in total (Example 7), TiO₂ and SrO, in an amount of 1.5 wt % in total(Example 8), TiO₂ and BaO, in an amount of 2.0 wt % in total (Example9), Fe₂ O₃ and MgO, in an amount of 2.5 wt % in total (Example 10), TiO₂and CaO which was different from CaO used as a stabilizer for ZrO₂, inan amount of 3.0 wt % in total (Example 11), and Fe₂ O₃ and TiO₂ in anamount of 0.5 wt % in total (Example 12).

The setting members thus obtained were satisfactory enough to berepeatedly employed in heating ferrite or a condenser for a number oftimes.

Hitherto, it is known that the setting member manufactured by using Al₂O₃ as the base and ZrO₂ as a main component of the coating material, isusually used for heating. In the coating material of such a settingmember, if an additional component previously mentioned was added evenin a small amount, an excellent setting member suitable for heatingferrite or a condenser was successfully obtained.

In Table 2, Comparative Examples 5 to 7 are shown. Of the particlesconstituting the coating material in these Comparative Examples,particles having a diameter of 0.1 mm or less were contained in anamount of 50 wt % or less. Comparative Example 7 employing MgO as a maincomponent and an additional component. Comparative Examples 5 to 7failed to provide a good setting member since particles of the coatingmaterial bonded to a condenser, as shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                        7    Al.sub.2 O.sub.3                                                                   80  ZrO.sub.2 --C                                                                      90 80      Fe.sub.2 O.sub.3                                                                  0.2                                                                       CaO 0.9                                         8    Al.sub.2 O.sub.3                                                                   80    "  92 85      TiO.sub.2                                                                         1.0                                                                       SrO 0.5                                         9    Al.sub.2 O.sub.3                                                                   85    "  91 90      TiO.sub.2                                                                         1.0                                                                       BaO 1.0                                        10    Al.sub.2 O.sub.3                                                                   85    "  87 75      Fe.sub.2 O.sub.3                                                                  0.5                                                                       MgO 2.0                                        11    Al.sub.2 O.sub.3                                                                   90    "  85 85      TiO.sub.2                                                                         1.0                                                                       CaO 2.0                                        12    Al.sub.2 O.sub.3                                                                   90    "  86 75      Fe.sub.2 O.sub.3                                                                  0.2                                                                       TiO.sub.2                                                                         0.3                                        Comparative                                                                   Example                                                                        5    Al.sub.2 O.sub.3                                                                   80  MgO  80 20      TiO.sub.2                                                                         2.0                                         6    Al.sub.2 O.sub.3                                                                   70  Al.sub.2 O.sub.3                                                                   98 30      Fe.sub.2 O.sub.3                                                                  1.0                                                                       CaO 1.0                                         7    Al.sub.2 O.sub.3                                                                   90  MgO  80 75      MgO 2.0                                                       Al.sub.2 O.sub.3                                                                   18                                                        __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                        7    98     124  82    No cracks until                                                                      Ferrite                                                                82 cycles                                              8    36     52   132   No cracks until                                                                      Condenser                                                              132 cycles                                             9    21     24   149   No cracks until                                                                      Condenser                                                              149 cycles                                            10    87     103  105   No cracks until                                                                      Ferrite                                                                105 cycles                                            11    42     57   120   No cracks until                                                                      Condenser                                                              120 cycles                                            12    146    173  64    No cracks until                                                                      Ferrite                                                                64 cycles                                             Comparative                                                                   Example                                                                        5    890    1280 No peeling                                                                          No cracks until                                                                      Condenser*3                                                      until 10                                                                            10 cycles                                                               cycles                                                       6    260    520  No peeling                                                                          No cracks until                                                                      Ferrite*4                                                        until 10                                                                            10 cycles                                                               cycles                                                       7    1580   2150 --    --     Ferrite*3                                      __________________________________________________________________________     *3 . . . Particles of coating material adhere on the heating material         *4 . . . Particles of coating material adhere on the heating material         after 8 cycles                                                           

(EXAMPLES 13-19, COMPARATIVE EXAMPLES 8-11)

The setting members were obtained by using materials shown in Table 3,in the same manner as in Examples 1-6. In Example 13, the same basematerial as that in Example 1 was used, Al₂ O₃ was used as a maincomponent and Fe₂ O₃ as an additional component of the coating material.The setting member of Example 13 containing an additional component evenin a small amount, heated ferrite 96 times. In Example 14 employing Al₂O₃ as a main component and a mixture of TiO₂ and BaO as an additionalcomponent of the coating material, a condenser experienced heating 160times. In Example 15 and 16, varister and ferrite were tolerable toheating 46 times and 48 times, respectively. The setting materialobtained by using MgO as a main component of the coating material, issuitable for heating a material containing PbO and Bi₂ O₃ since ithardly react with other materials.

Example 17 and 18 employed Al₂ O₃ and ZrO₂ stabilized with CaO as a maincomponent of the coating material. Example 19 employed Al₂ O₃ and MgO asa main component of the coating material. In any one of cases, a goodresult was obtained in ferrite heating. In Comparative Examples listedin Table 3, the main component of the coating material was used in anamount of 80 wt % or less. In these cases, after heating, no desiredproperties as ferrite, condenser and varister were obtained andtherefore, the setting member obtained in Comparative Examples were notput into a practical use.

                                      TABLE 3                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       13    Al.sub.2 O.sub.3                                                                   72  Al.sub.2 O.sub.3                                                                    95                                                                              60      Fe.sub.2 O.sub.3                                                                  3.0                                        14    Al.sub.2 O.sub.3                                                                   72  Al.sub.2 O.sub.3                                                                    94                                                                              60      TiO.sub.2                                                                         3.0                                                                       BaO 2.0                                        15    Al.sub.2 O.sub.3                                                                   90  MgO   97                                                                              80      TiO.sub.2                                                                         2.0                                        16    Al.sub.2 O.sub.3                                                                   90  MgO   90                                                                              90      Fe.sub.2 O.sub.3                                                                  8.0                                        17    Al.sub.2 O.sub.3                                                                   90  ZrO.sub.2 --C                                                                       86                                                                              80      Fe.sub.2 O.sub.3                                                                  0.6                                                       Al.sub.2 O.sub.3                                                                     2        BaO 0.6                                        18    Al.sub.2 O.sub.3                                                                   80  ZrO.sub.2 --C                                                                       20                                                                              65      Fe.sub.2 O.sub.3                                                                  0.8                                                       Al.sub.2 O.sub.3                                                                    78        SrO 0.8                                        19    Al.sub.2 O.sub.3                                                                   80  Al.sub.2 O.sub.3                                                                    20                                                                              80      Fe.sub.2 O.sub.3                                                                  1.0                                                       MgO   76                                                       Comparative                                                                   Example                                                                        8    Al.sub.2 O.sub.3                                                                   90  ZrO.sub.2 --C                                                                       75                                                                              60      Fe.sub.2 O.sub.3                                                                  5.0                                         9    Al.sub.2 O.sub.3                                                                   85  ZrO.sub.2 --C                                                                       65                                                                              60      TiO.sub.2                                                                         5.0                                        10    Al.sub.2 O.sub.3                                                                   72  Al.sub.2 O.sub.3                                                                    75                                                                              60      Fe.sub.2 O.sub.3                                                                  3.0                                        11    Al.sub.2 O.sub.3                                                                   90  MgO   70                                                                              80      TiO.sub.2                                                                         2.0                                        __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       13    82     104  96    No cracks until                                                                      Ferrite                                                                96 cycles                                             14    10     18   160   No cracks until                                                                      Condenser                                                              160 cycles                                            15    40     54   46    No cracks until                                                                      Varister                                                               46 cycles                                             16    64     92   48    No cracks until                                                                      Ferrite                                                                48 cycles                                             17    20     28   132   No cracks until                                                                      Ferrite                                                                132 cycles                                            18    44     58   148   No cracks until                                                                      Ferrite                                                                148 cycles                                            19    92     121  53    No cracks until                                                                      Ferrite                                                                53 cycles                                             Comparative                                                                   Example                                                                        8    70     --   --    --     Ferrite                                                                       No desired                                                                    properties                                      9    41     --   --    --     Condenser                                                                     No desired                                                                    properties                                     10    50     --   --    --     Ferrite                                                                       No desired                                                                    properties                                     11    28     --   --    --     Varister                                                                      No desired                                                                    properties                                     __________________________________________________________________________

(EXAMPLES 20-25, AND COMPARATIVE EXAMPLES 12-15)

The setting members were obtained by using materials shown in Table 4,in the same manner as in Examples 1-6. In Example 20, MgO was employedas a main component of the base and rest was CaO and an inevitablycontained component. The main component of the coating material wasunstabilized ZrO₂, and Fe₂ O₃ was used as an additional component of thecoating material. Ferrite was able to be heated 105 times by using thesetting member obtained in the above.

Example 21, ZrO₂ partially stabilized with CaO was used as a maincomponent of the coating material, TiO₂ was used as an additionalcomponent. In this case, a good heating result was obtained with respectto a condenser.

Example 22, MgO was used as main components of the base and the coatingmaterial, and BaO was used as an additional component.

In Example 23, the main component of the base was MgO, a main componentof the coating material was a mixture of MgO and ZrO₂ partiallystabilized MgO, and SrO was added as an additional component. Althoughheating record was as low as 28 times, the coating layer of Example 23was superior to that containing no additional components.

Example 24 employed MgO as a main component of the base, Al₂ O₃ as amain component of the coating material, and MgO as an additionalcomponent of the coating material.

Example 25 employed MgO as a main component of the base, Al₂ O₃ as amain component of the coating material, and Fe₂ O₃ as an additionalcomponent of the coating material. In any one of the cases, good heatingrecord was obtained.

Comparative Examples are also listed in Table 4. Comparative Examples 12and 13 employed an additional component in an amount smaller than therange limited by the present invention. On the contrary, the amount ofan additional component employed in Comparative Examples 14 and 15exceeded the range. In any one of the case, the coating layer was peeledoff after heated a few times. Therefore the setting members obtained inthese Comparative Examples are not suitable for putting into practicaluse.

                                      TABLE 4                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       20    MgO  80  ZrO.sub.2 --N*5                                                                     80                                                                              70      Fe.sub.2 O.sub.3                                                                  6.0                                        21    MgO  85  ZrO.sub.2 --C                                                                       83                                                                              65      TiO.sub.2                                                                         4.0                                        22    MgO  90  MgO   98                                                                              75      BaO 1.0                                        23    MgO  95  MgO   79                                                                              75      SrO 10.0                                                      ZrO.sub.2 --M*6                                                                     10                                                       24    MgO  70  Al.sub.2 O.sub.3                                                                    83                                                                              80      MgO 5.0                                        25    MgO  75  Al.sub.2 O.sub.3                                                                    93                                                                              80      Fe.sub.2 O.sub.3                                                                  4.0                                        Comparative                                                                   Example                                                                       12    Al.sub.2 O.sub.3                                                                   80  ZrO.sub.2 --C                                                                       87                                                                              65      SrO 0.2                                        13    MgO  85  Al.sub.2 O.sub.3                                                                    90                                                                              70      TiO.sub.2                                                                         0.3                                                       MgO    2                                                       14    Al.sub.2 O.sub.3                                                                   77  ZrO.sub.2 --C                                                                       80                                                                              70      Fe.sub.2 O.sub.3                                                                  15.0                                       15    Al.sub.2 O.sub.3                                                                   80  ZrO.sub.2 --N                                                                       84                                                                              100     CaO 15.0                                       __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       20    48     59   105   No cracks until                                                                      Ferrite                                                                105 cycles                                            21    38     50   48    No cracks until                                                                      Condenser                                                              48 cycles                                             22    78     110  41    No cracks until                                                                      Condenser                                                              41 cycles                                             23    36     52   28    No cracks until                                                                      Condenser                                                              28 cycles                                             24    96     140  60    No cracks until                                                                      Ferrite                                                                60 cycles                                             25    61     70   102   No cracks until                                                                      Ferrite                                                                102 cycles                                            Comparative                                                                   Example                                                                       12    890    1500 --    --     Condenser*3                                    13    420    610  No peeling                                                                          No cracks until                                                                      Condenser*7                                                      until 10                                                                            10 cycles                                                               cycles                                                      14     5     --   --    --     Ferrite                                                                       No desired                                                                    properties                                     15    132    --   --    --     Ferrite                                                                       No desired                                                                    properties                                     __________________________________________________________________________     *5 ZrO.sub.2 --N . . . Unstabilized ZrO.sub.2 -                               *6 ZrO.sub.2 --M . . . ZrO.sub.2 partially stabilized with MgO                *3 . . . Particles of coating material adhere on the heating material         *7 . . . Particles of coating material adhere on the heating material         after 5 cycles                                                           

(EXAMPLES 26-29)

The setting members were obtained by using materials shown in Table 5,in the same manner as in Examples 1-6. Examples 26-29 employed two typesof compounds as a main component of the base.

Example 26 employed a mixture of MgO and Al₂ O₃ as a main component ofthe base. In Example 27, a mixture of Al₂ O₃ and unstabilized ZrO₂ wasused as main component of the base. In Example 28, a main component ofthe base was a mixture of ZrO₂ partially stabilized with CaO and MgO,and a main component of the coating material was ZrO₂ partiallystabilized with CaO.

In Example 29, a main component of the base was a mixture of MgO and Al₂O₃ and ZrO₂ partially stabilized with Y₂ O₃, and the main component ofthe coating layer was ZrO₂ partially stabilized with Y₂ O₃. Any of thesetting members obtained in these Examples is excellent as shown inTable 5.

                                      TABLE 5                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       26    MgO  60  MgO   80                                                                              90      Fe.sub.2 O.sub.3                                                                  2.0                                              Al.sub.2 O.sub.3                                                                   20                                                                 27    Al.sub.2 O.sub.3                                                                   50  Al.sub.2 O.sub.3                                                                    80                                                                              90      BaO 2.0                                              ZrO.sub.2 --N                                                                      30                                                                 28    ZrO.sub.2 --C                                                                      50  ZrO.sub.2 --C                                                                       80                                                                              90      SrO 3.0                                              MgO  30                                                                 29    MgO  70  ZrO.sub.2 --Y*8                                                                     95                                                                              80      TiO.sub.2                                                                         2.0                                              Al.sub.2 O.sub.3                                                                   15                                                                       ZrO.sub.2 --Y                                                                      10                                                                 __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       26    76     114  51    No cracks until                                                                      Ferrite                                                                51 cycles                                             27    38     49   89    No cracks until                                                                      Condenser                                                              89 cycles                                             28    72     99   85    No cracks until                                                                      Condenser                                                              85 cycles                                             29    30     38   125   No cracks until                                                                      Condenser                                                              125 cycles                                            __________________________________________________________________________     *8 ZrO.sub.2 --Y . . . ZrO.sub.2 partially stabilized with Y.sub.2 O.sub.                                                                              

(EXAMPLES 30-35)

The setting members were obtained by using materials shown in Table 6,in the same manner as in Examples 1-6. The setting members of Examples30-35 employed ZrO₂, at least part of which was partially stabilizedwith a stabilizer, as a main component of the base.

In Example 30, ZrO₂ partially stabilized with CaO was used as a maincomponent of the base and Al₂ O₃ was a main component of the coatingmaterial to which Fe₂ O₃ was added as an additional component.

Example 31 employed ZrO₂ partially stabilized with Y₂ O₃ as a maincomponent of the base and unstabilized ZrO₂ as a main component of thecoating material.

In Example 32, ZrO₂ partially stabilized with MgO was used as a maincomponent of the base and unstabilized ZrO₂ as a main component of thecoating material. Further, as an additional component, use was made ofMgO, which was different from MgO used as a stabilizer for ZrO₂.

In all setting members obtained above, abrasion resistance and peelresistance were satisfactory.

In Example 33, a mixture of ZrO₂ partially stabilized with CaO and ZrO₂partially stabilized with Y₂ O₃ was used as a main component of the baseand the main component of the coating material was MgO and additionalcomponent was SrO.

Example 34 employed a mixture of ZrO₂ partially stabilized with CaO andunstabilized ZrO₂ as a main component of the base.

In Example 35, the main component of the base was a mixture of ZrO₂partially stabilized with Y₂ O₃ and unstabilized ZrO₂.

The main components of the coating materials of Examples 33 and 34 wereMgO and unstabilized ZrO₂, respectively. The setting members obtained inExamples 33 and 34 were excellent.

Comparative Examples 16 and 17 are similar to Examples 34 and 35 exceptthat the Comparative Examples contain no additional components. In thesetting members obtained in Comparative Examples 16 and 17, a largeabrasion amount was obtained after heating and particles of the coatinglayer were bonded onto a condenser, so that they was not practicallyused. As is apparent from the above, the effect of the additionalcomponent is remarkably excellent.

                                      TABLE 6                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       30    ZrO.sub.2 --C                                                                      80  Al.sub.2 O.sub.3                                                                    85                                                                              80      Fe.sub.2 O.sub.3                                                                  3.0                                        31    ZrO.sub.2 --Y                                                                      95  ZrO.sub.2 --N                                                                       97                                                                              60      TiO.sub.2                                                                         2.0                                        32    ZrO.sub.2 --M                                                                      70  ZrO.sub.2 --N                                                                       73                                                                              70      BaO 1.0                                                       MgO   25                                                       33    ZrO.sub.2 --C                                                                      70  MgO   80                                                                              70      SrO 4.0                                              ZrO.sub.2 --Y                                                                      25                                                                 34    ZrO.sub.2 --C                                                                      40  ZrO.sub.2 --N                                                                       96                                                                              75      CaO 3.0                                              ZrO.sub.2 --N                                                                      40                                                                 35    ZrO.sub.2 --Y                                                                      65  ZrO.sub.2 --N                                                                       94                                                                              70      MgO 5.0                                              ZrO.sub.2 --N                                                                      30                                                                 Comparative                                                                   Example                                                                       16    ZrO.sub.2 --C                                                                      40  ZrO.sub.2 --N                                                                       96                                                                              75      None                                                 ZrO.sub.2 --N                                                                      40                                                                 17    ZrO.sub.2 --Y                                                                      65  ZrO.sub.2 --N                                                                       94                                                                              70      None                                                 ZrO.sub.2 --N                                                                      30                                                                 __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       30    52      58  84    No cracks until                                                                      Ferrite                                                                84 cycles                                             31    80     118  102   No cracks until                                                                      PCT                                                                    102 cycles                                                                           thermistor                                     32    104    162  40    No cracks until                                                                      Condenser                                                              40 cycles                                             33    96     150  36    No cracks until                                                                      Condenser                                                              36 cycles                                             34    120    206  120   No cracks until                                                                      Condenser                                                              120 cycles                                            35    180    315  80    No cracks until                                                                      Condenser                                                              80 cycles                                             Comparative                                                                   Example                                                                       16    2500   --   --    --     Condenser*3                                          or more*9                                                               17    2600   --   --    --     Condenser*3                                          or more*9                                                               __________________________________________________________________________     *3 . . . Particles of coating material adhere on the heating material         *9 . . . Abrasion proceeded to a base material                           

(EXAMPLES 36-43)

The setting members were obtained by using materials shown in Table 7,in the same manner as in Examples 1-6. In Example 36, a main componentof the base was Al₂ O₃, a main component of the coating material wasunstabilized ZrO₂ and an additional component was MgO. In this case,even if Mgo serving as an additional component was added in an amount aslarge as 6.0 wt %, heating times until the coating material was peeledoff, were recorded as large as 120 times.

Example 37, CaO was added as an additional component in an amount of 7.0wt %.

Examples 38-43, three types of additional components were used.

Any setting member obtained above is excellent in heating record, as isapparent from Table 7.

                                      TABLE 7                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       36    Al.sub.2 O.sub.3                                                                   93  ZrO.sub.2 --N                                                                       85                                                                              65      MgO 6.0                                        37    Al.sub.2 O.sub.3                                                                   80  ZrO.sub.2 --C                                                                       45                                                                              70      CaO 7.0                                                       ZrO.sub.2 --Y                                                                       45                                                       38    Al.sub.2 O.sub.3                                                                   85  ZrO.sub.2 --C                                                                       85                                                                              65      BaO 4.0                                                                       TiO.sub.2                                                                         3.0                                                                       CaO 3.0                                        39    Al.sub.2 O.sub.3                                                                   98  ZrO.sub.2 --N                                                                       95                                                                              100     BaO 0.5                                                                       TiO.sub.2                                                                         2.0                                                                       CaO 2.0                                        40    Al.sub.2 O.sub.3                                                                   75  ZrO.sub.2 --C                                                                       30                                                                              70      BaO 3.0                                                       ZrO.sub.2 --N                                                                       60        TiO.sub.2                                                                         2.0                                                                       CaO 1.0                                        41    Al.sub.2 O.sub.3                                                                   75  ZrO.sub.2 --C                                                                       30                                                                              70      SrO 3.0                                                       ZrO.sub.2 --N                                                                       60        TiO.sub.2                                                                         2.0                                                                       CaO 1.0                                        42    Al.sub.2 O.sub.3                                                                   85  ZrO.sub.2 --C                                                                       85                                                                              65      SrO 4.0                                                                       TiO.sub.2                                                                         3.0                                                                       CaO 3.0                                        43    Al.sub.2 O.sub.3                                                                   98  ZrO.sub.2 --N                                                                       95                                                                              100     SrO 0.5                                                                       TiO.sub.2                                                                         2.0                                                                       CaO 2.0                                        __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       36    120    160  120   No cracks until                                                                      Condenser                                                              120 cycles                                            37    52     61    85   No cracks until                                                                      Condenser                                                              85 cycles                                             38     5     16   134   No cracks until                                                                      Condenser                                                              134 cycles                                            39    25     44   160   No cracks until                                                                      Condenser                                                              160 cycles                                            40     5     18   152   No cracks until                                                                      Condenser                                                              152 cycles                                            41    32     56   144   No cracks until                                                                      Condenser                                                              144 cycles                                            42    28     46   105   No cracks until                                                                      Varister                                                               105 cycles                                            43    32     48   148   No cracks until                                                                      PCT                                                                    148 cycles                                                                           thermistor                                     __________________________________________________________________________

(EXAMPLES 44-51)

The setting members were obtained by using materials shown in Table 8,in the same manner as in Examples 1-6. In each of Examples 44-49, a maincomponent of the coating material was partially stabilized ZrO₂ orunstabilized ZrO₂. In these cases, two types of compounds were used asthe additional component, the resultant coating layers were excellent inpeel resistance. In Example 49, a varister was used as a heatingmaterial. The result of the heating was excellent. Examples 50-51, twotypes of components are used as the main component and as the additionalcomponent of the coating material. Example 52 employed three types ofadditional components. In any setting member mentioned above, excellentresults were obtained.

                                      TABLE 8                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of Particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       44    Al.sub.2 O.sub.3                                                                   90  ZrO.sub.2 --C                                                                       90                                                                              75      BaO 5.0                                                                       TiO.sub.2                                                                         3.0                                        45    Al.sub.2 O.sub.3                                                                   98  ZrO.sub.2 --Y                                                                       90                                                                              80      BaO 2.0                                                                       TiO.sub.2                                                                         3.0                                        46    Al.sub.2 O.sub.3                                                                   99  ZrO.sub.2 --N                                                                       96                                                                              80      SrO 2.0                                                                       TiO.sub.2                                                                         1.0                                        47    Al.sub.2 O.sub.3                                                                   99  ZrO.sub.2 --N                                                                       96                                                                              80      BaO 2.0                                                                       TiO.sub.2                                                                         1.0                                        48    Al.sub.2 O.sub.3                                                                   90  ZrO.sub.2 --C                                                                       90                                                                              75      SrO 5.0                                                                       TiO.sub.2                                                                         3.0                                        49    Al.sub.2 O.sub.3                                                                   98  ZrO.sub.2 --Y                                                                       90                                                                              80      SrO 2.0                                                                       TiO.sub.2                                                                         3.0                                        50    Al.sub.2 O.sub.3                                                                   95  ZrO.sub.2 --C                                                                       60                                                                              60      SrO 7.0                                                       ZrO.sub.2 --N                                                                       28        TiO.sub.2                                                                         3.0                                        51    Al.sub.2 O.sub.3                                                                   95  ZrO.sub.2 --C                                                                       60                                                                              60      BaO 7.0                                                       ZrO.sub.2 --N                                                                       28        TiO.sub.2                                                                         3.0                                        52    Al.sub.2 O.sub.3                                                                   99  ZrO.sub.2 --N                                                                       96                                                                              80      BaO 1.0                                                                       SrO 1.0                                                                       TiO.sub.2                                                                         3.0                                        __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       44    10     15   126   No cracks until                                                                      Condenser                                                              126 cycles                                            45     5     13   146   No cracks until                                                                      Condenser                                                              146 cycles                                            46    45     54   128   No cracks until                                                                      PCT                                                                    128 cycles                                                                           thermistor                                     47    10     22   136   No cracks until                                                                      Condenser                                                              136 cycles                                            48    46     60   101   No cracks until                                                                      Condenser                                                              101 cycles                                            49    35     44   132   No cracks until                                                                      Varister                                                               132 cycles                                            50    52     65   No peeling                                                                          No cracks until                                                                      Condenser                                                        until 84                                                                            84 cycles                                                               cycles                                                      51    10     18   No peeling                                                                          No cracks until                                                                      Condenser                                                        until 92                                                                            92 cycles                                                               cycles                                                      52    15     26   140   No cracks until                                                                      Condenser                                                              140 cycles                                            __________________________________________________________________________

(Examples 53-58)

The setting members were obtained by using materials shown in Table 9,in the same manner as in Examples 1-6. In all Examples shown in Table 9,the main component of the base was Al₂ O₃ and a main component of thecoating material was partially stabilized ZrO₂ (Example 53),unstabilized ZrO₂ (Example 54), and a mixture of partially stabilizedZrO₂, and unstabilized ZrO₂ (Example 55). The two types of additionalcomponents were used in the coating material as shown in Table 9.Furthermore, Examples 56-58, Al₂ O₃ was used as the main components ofthe base and of the coating material. The additional components are Fe₂O₃ (Example 56), Fe₂ O₃ and CaO (Example 57), and TiO₂ (Example 58). Inall cases mentioned above, excellent results were obtained in a heatingtest of a condenser or ferrite.

                                      TABLE 9                                     __________________________________________________________________________                   Coating Material Component                                                            Rate of particles                                                                     Additional                                           Base Component                                                                         Main Component                                                                        of 0.1 mm or less                                                                     Component                                      No.   (wt. %)  (wt. %) (wt. %) (wt. %)                                        __________________________________________________________________________    Example                                                                       53    Al.sub.2 O.sub.3                                                                   90  ZrO.sub.2 --C                                                                       95                                                                              80      Fe.sub.2 O.sub.3                                                                  1.0                                                                       CaO 5.0                                        54    Al.sub.2 O.sub.3                                                                   75  ZrO.sub.2 --N                                                                       85                                                                              75      Fe.sub.2 O.sub.3                                                                  1.0                                                                       CaO 0.5                                        55    Al.sub.2 O.sub.3                                                                   80  ZrO.sub.2 --C                                                                       80                                                                              70      Fe.sub.2 O.sub.3                                                                  3.0                                                       ZrO.sub.2 --N                                                                       15        CaO 1.0                                        56    Al.sub.2 O.sub.3                                                                   70  Al.sub.2 O.sub.3                                                                    89                                                                              60      Fe.sub.2 O.sub.3                                                                  10.0                                       57    Al.sub.2 O.sub.3                                                                   75  Al.sub.2 O.sub.3                                                                    96                                                                              55      Fe.sub.2 O.sub.3                                                                  2.0                                                                       CaO 1.0                                        58    Al.sub.2 O.sub.3                                                                   90  Al.sub.2 O.sub.3                                                                    97                                                                              60      TiO.sub.2                                                                         2.0                                        __________________________________________________________________________    Evaluation of Setting Member for Heating Material                                          Evaluation at Heating Cycle                                                   Specific                                                                           Heating                                                                             Heating                                                     Specific                                                                             Abrasion                                                                           Cycles for                                                                          Cycles for                                                                           Heating                                              Abrasion                                                                             Amount                                                                             Removing                                                                            Generating                                                                           Material                                             Amount after                                                                              Entire                                                                              Crack  and                                                  after Heating                                                                        heating                                                                            Coating                                                                             on Setting                                                                           Relevancy                                      No.   (mg/Kgf · cm)                                                               (10 times)                                                                         Layer Member thereof                                        __________________________________________________________________________    Example                                                                       53    24     38    82   No cracks until                                                                      Ferrite                                                                82 cycles                                             54    10     18   154   No cracks until                                                                      Ferrite                                                                154 cycles                                            55     5     10   163   No cracks until                                                                      Ferrite                                                                163 cycles                                            56    46     49   No peeling                                                                          No cracks until                                                                      Ferrite                                                          until 120                                                                           120 cycles                                                                           Properties                                                       cycles       deteriorate at                                                                120th cycle                                    57    10     20   196   No cracks until                                                                      Ferrite                                                                196 cycles                                            58    30     36   105   No cracks until                                                                      Condenser                                                              105 cycles                                            __________________________________________________________________________

What is claimed is:
 1. A setting member for a heating materialcomprising a base and a coating layer formed on a surface of said basepartially or in its entirety, wherein said base comprises at least onemain component selected from the group consisting of Al₂ O₃, MgO andZrO₂ in an amount of 70 wt % or more and said coating layer comprises atleast one main component selected from the group consisting of Al₂ O₃,MgO and ZrO₂ in an amount of 80 wt % or more, and 0.5 to 10.0 wt % of atleast one additional component selected from the group consisting of Fe₂O₃, TiO₂, BaO, SrO, CaO and MgO, wherein if CaO or MgO are used tostabilize ZrO, as a main component of the coating layer, then the CaOand MgO that can be additional components are used in addition to theCaO or MgO used to stabilize the ZrO₂.
 2. The setting member for aheating material according to claim 1, wherein a main component of saidbase comprises at least one selected from the group consisting of ZrO₂partially stabilized with CaO, ZrO₂ partially stabilized with MgO, andZrO₂ partially stabilized with Y₂ O₃.
 3. The setting member for aheating material according to claim 1, wherein a main component of saidbase comprises unstabilized ZrO₂ and at least one selected from thegroup consisting of ZrO₂ partially stabilized with CaO, ZrO₂ partiallystabilized with MgO, and ZrO₂ partially stabilized with Y₂ O₃.
 4. Thesetting member for a heating material according to claim 1, wherein saidbase comprises Al₂ O₃ as a main component and a coating layer comprisesAl₂ O₃ as a main component and Fe₂ O₃ as an additional component.
 5. Thesetting member for a heating material according to claim 1, wherein saidbase comprises Al₂ O₃ as a main component, said coating layer comprisesAl₂ O₃ as a main component and Fe₂ O₃ and CaO as an additionalcomponent.
 6. The setting member for a heating material according toclaim 1, wherein said base comprises Al₂ O₃ as a main component and saidcoating layer comprises Al₂ O₃ as a main component and TiO₂ as anadditional component.
 7. The setting member for a heating materialaccording to claim 1, wherein said base comprises Al₂ O₃ as a maincomponent, said coating layer comprises unstabilized ZrO₂ and/orpartially stabilized ZrO₂ as a main component, and BaO and/or SrO, andTiO₂ as an additional component.
 8. The setting member for a heatingmaterial according to claim 1, wherein said base comprises Al₂ O₃ as amain component, said coating layer comprises unstabilized ZrO₂ and/orpartially stabilized ZrO₂ as a main component, and BaO and/or SrO, TiO₂and CaO as an additional component.
 9. The setting member for a heatingmaterial according to claim l, wherein said base comprises Al₂ O₃ as amain component, said coating layer comprises unstabilized ZrO₂ and/orpartially stabilized ZrO₂ as a main component, and Fe₂ O₃ and CaO as anadditional component.
 10. The setting member for a heating materialaccording to claim 1, wherein said coating layer comprises at least onemain component selected from the group consisting of ZrO₂ stabilizedwith MgO, ZrO₂ stabilized with CaO, and ZrO₂ stabilized with Y₂ O₃. 11.The setting member for a heating material according to claim 1, whereinsaid coating layer comprises an unstabilized ZrO₂ and at least oneselected from the group consisting of ZrO₂ stabilized with MgO, ZrO₂stabilized with CaO, and ZrO₂ stabilized with Y₂ O₃ as a main component.12. The setting member for a heating material according to claim 1,wherein ZrO₂ used as a main component of said coating layer isunstabilized ZrO₂.
 13. The setting member for a heating materialaccording to claim 1, wherein said coating layer comprises particleshaving 0.1 mm in diameter or less in an amount of 50 wt % or more.